Color image reproduction systems known in the art permit images to be captured by certain image-receptive media or devices, possibly digitized and stored, and then outputted onto a complementary medium. For instance, color images may be first captured on negative photographic film and then reproduced on negative photographic paper. The negative film may be printed directly onto the photographic paper, or the negative film may be photodigitized to form a digital intermediary image. In either application, the printing of the image onto the photographic paper must be controlled so as to produce prints that are properly balanced for color.
Color imaging systems in which the image passes through a digital intermediary allow adjustments to be made to the image using a single means, which may be a digital computer equipped with a suitable video display. If the video display is proceeded by the appropriate signal processing, adjustments to the density and color balance of a displayed image can be made in a way that previews corresponding adjustments to the final image produced from the digital intermediary. Similar image-previewing features can be realized on color-imaging systems in which the image does not pass through a digital intermediary. For example, an image recorded on a photographic film may be converted to a video image by analog or digital means. Adjustments may then be made to the video image, and a record of these adjustments may be retained. These adjustments can then be used to control the settings of an optical printer used to print the photographic image onto a photographic paper or other suitable image-receptive medium. Systems incorporating these features are well known to those skilled in the art.
The success of these techniques is dependent, to a significant degree, on the skill of the operator performing the adjustments. In many cases, it is difficult for an operator to notice small differences in color balance on a video display, although these differences may appear significant on the final reproduced image. Operator errors may be due to lack of skill, fatigue, and other factors such as localized chromatic adaptation. If a color-imaging system provided a means of enhancing the visibility of small color balance differences, that system would simplify the color-balancing process and provide for greater color-balance accuracy and consistency.